Although the [100] direction is the most suitable to droplet thermal migration because of such factors as droplet stability and the ease of droplet penetration at the starting (100) vacuum-solid interface, it has been found in some instances that droplets migrated in that direction suffer relatively large mean square displacement. While this effect is comparatively small in both low and high density dislocation crystals, it is large enough in those of medium dislocation density (i.e., from 5 .times. 10.sup.4 to 5 .times. 10.sup.7 dislocations per square centimeter) to prevent production of relatively straight droplet migration trails and thus precludes the production of regular deep diode P-N junction arrays by the otherwise preferred [100] axis migration mode. Neither droplet size or mass nor maximum temperature or thermal gradient have any significant effect on this phenomenon.